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File:Hertzian spark radio transmitter 1902.jpg

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Hertzian_spark_radio_transmitter_1902.jpg (637 × 453 pixels, file size: 91 KB, MIME type: image/jpeg)

Summary

Description
English: A Hertzian spark gap transmitter used in 1902 by Archie Frederick Collins (in picture) to investigate brain response to radio waves. This was the earliest type of radio transmitter, very similar to the ones Heinrich Hertz used in 1887 to discover radio waves. It consists of a half wave dipole antenna made of two horizontal wires ending in metal plates (E) with a spark gap (D) between them. When the operator presses the telegraph key switch (C), current from the automotive type lead-acid battery (B, bottom) powers the induction coil transformer (A) which produces pulses of high voltage which are applied to the spark gap. Sparks across the spark gap excite standing waves of current in the antenna, which radiates radio waves.

The dimensions of the antenna, acting as a half-wave dipole, determine the frequency of the radio waves generated. Since it is roughly one meter long, the radio waves have a wavelength of about 2 meters, resulting in a frequency of about 150 MHz; about the frequency used today by FM radio stations.
Alterations to image: partially removed aliasing artifacts (crosshatched lines) caused by scanning of halftone photo, using Fourier transform filter in Gimp image editor.
Date
Source Retrieved January 26, 2018 from Archie Frederick Collins "The effect of electric waves on the human brain", in Electrical World and Engineer magazine, Vol. 39, No. 8, February 22, 1902, p. 335, fig. 2 on Google Books.
Author Archie Frederick Collins

Licensing

Public domain
This work is in the public domain in the United States because it was published (or registered with the U.S. Copyright Office) before January 1, 1929.

Public domain works must be out of copyright in both the United States and in the source country of the work in order to be hosted on the Commons. If the work is not a U.S. work, the file must have an additional copyright tag indicating the copyright status in the source country.
Note: This tag should not be used for sound recordings.PD-1923Public domain in the United States//commons.wikimedia.org/wiki/File:Hertzian_spark_radio_transmitter_1902.jpg
Annotations
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Captions

Early experimental Hertzian spark radio transmitter from 1902

Items portrayed in this file

depicts

22 February 1902Gregorian

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Date/TimeThumbnailDimensionsUserComment
current17:38, 1 May 2021Thumbnail for version as of 17:38, 1 May 2021637 × 453 (91 KB)MaterialscientistFFT
03:08, 27 January 2018Thumbnail for version as of 03:08, 27 January 2018637 × 453 (56 KB)ChetvornoUser created page with UploadWizard

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